1. Field of the Invention
The present invention generally relates to a structure for preventing electrical leakage in an electric power tool, and more particularly, to a structure for preventing electrical leakage for use in an electric power tool provided with a commutator motor which is encased in a metal housing.
2. Description of the Related Art
Some electric power tools are provided with a housing made of metal, such as iron or aluminum, to provide sufficient strength against shock and vibration. These electric power tools typically have a commutator motor encased in such a metal housing and a pair of brush holders which press a pair of brushes against the motor to supply power. Additionally, such a tool includes a fan that rotates with the motor to draw air from the outside through air inlets formed in the housing to cool the motor.
While adequate for the purpose intended, this structure for cooling the motor of an electric power tool has certain inherent disadvantages or deficiencies if the tool is a grinder or other device or appliance that generates metal powder, such as iron power, during operation. Ground metal powder is drawn inside the housing and a portion thereof adheres to and is deposited on the brush holders without exiting the tool through air outlets which are provided in the housing. In some cases, the metal power deposit electrically bridges the conductive parts of the brush holders and the housing, thus causing electrical leakage into the housing.